A conventional ball valve is disclosed in, e.g., Japanese Published Unexamined Utility-Model Application No. Sho 59-188360. In the conventional ball valve, a valve chamber with entrance and exit communicating with each other in a casing is formed, a valve ball with a circulation hole is provided in the valve chamber, and an entrance-side ring valve seat is provided on the entrance side of the valve ball while an exit-side ring valve seat is provided on the exit side of the valve ball. The entrance and exit are connected or disconnected by rotating the valve ball with a valve shaft hermetically passing through the casing.
In the above-described conventional ball valve, the entrance and exit are connected/disconnected by rotate-operating the valve ball. However, the conventional ball valve lacks the capability of discharging fluid at its entrance from a discharge orifice communicating ambient air different from the entrance and exit, and/or releasing remaining pressure at its exit. For this reason, it is impossible to check the discharging state of a steam trap provided on the primary side and/or to release remaining pressure on the secondary side.
Accordingly, the purpose of the present invention is to provide a ball valve which enables the discharge of fluid in its entrance from a discharge orifice communicating ambient air different from the entrance and exit, and/or the release of remaining pressure in the exit side of the ball valve.